Flame tubes for gas turbine engines

ABSTRACT

A flame tube for a gas turbine engine includes a plurality of primary combustion air inlets, a plurality of secondary combustion air inlets and a plurality of dilution air inlets and variable flow restricting means associated with at least some of the inlets for varying the ratio of primary combustion air to secondary combustion air to dilution air.

United'States Patent Inventors Kenneth Greenwood Burnley;

Alban Heaton, Gt. Harwood, near Blackburn; Alwin Harrison; Squire Ronald Jackson, Burnley, England Dec. 11, 1968 May 1 1, 1971 Joseph Lucas (Industries) Limited Birmingham, England App]. No. Filed Patented Assignee FLAME TUBES FOR GAS TURBINE ENGINES 5 Claims, 26 Drawing Figs.

US. Cl 60/39.65, 60/3923, 60/3929 Int. Cl F02c 9/14 Field of Search 60/3965,

[56] References Cited UNITED STATES PATENTS 2,446,059 7/1948 Peterson et a1. 60/39.65X 2,457,157 12/1948 King 60/3923 2,618,120 11/1952 Papini 60/39.65X 2,684,573 7/ 1954 Marskell et a1. 60/3923 2,812,637 11/1957 Fox 60/39.23X 2,837,894 6/1958 Kind 60/3927 3,078,672 2/1963 Meurer 60/39.65X

, FOREIGN PATENTS 539,069 8/ 1941 Great Britain 60/3965 Primary Examiner-Douglas Hart Attorney-Holman, Glascock, Downing and Seebold ABSTRACT: A flame tube for a gas turbine engine includes a plurality of primary combustion air inlets, a plurality of secondary combustion air inlets and a plurality of dilution air inlets and variable flow restricting means associated with at least some of the inlets for varying the ratio of primary combustion air to secondary combustion air to dilution air.

Patentd -May 11, 1971 I 3,577,878

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18 Sheets-Sheet 18 \IIIIIIIIIIIIIIIIII -INVENTOE MW,%//m,%mm/flnw/ m ATTORNEY FLAME TUBES FOR GAS TURBINE ENGINES BACKGROUND OF THE INVENTION This invention relates to flame tubes for gas turbine engines.

In the flame tubes of such engines, it is the practice for a minor amount of air, about 2540 percent of the total air intake, to be employed for .the combustion of fuel, with the remainder being employed for cooling the flame tube, diluting of the flame and of the products of combustion before the latter are allowed to enter the turbine stage of the engine. The air for combustion purposes is itself normally separated into primary and secondary streams entering along separate paths to the interior of the flame tube. In some engines which are required to operate over a wide range of fuel/air ratios, the combustion and dilution air quantities over some parts of the operating range are incorrect thus impairing combustion and dilution air quantities over some parts of the operating range are incorrect thus impairing combustion efficiency and giving rise to loss of performance over that part of the engine operatmg range.

The object of the invention is to provide a flame tube for a gas turbine engine in which this disadvantage is overcome or reduced.

In accordance with the invention there is provided a flame tube for a gas turbine engine having a plurality of primary combustion air inlets, a plurality of secondary combustion air inlets, a plurality of dilution air inlets and variable airflow restricting means associated with at least some of said inlets for varying the ratio of primary combustion air to secondary combustion air to dilution air. Reference is now made to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial section through an annular flame tube incorporating one example of the present invention,

FIG. 2 is a view on the arrow X in FIG. I,

FIG. 3 is a fragmentary view on the arrow Y in FIG. 2,

FIG. 4 is a pneumatic circuit diagram illustrating the manner in which the arrangement shown in FIGS. I, 2, 3 is operated,

FIG. 5 is a section through an annular flame tube illustrating another embodiment of the present invention,

FIG. 6 is a fragmentary front view of the arrangement shown in FIG. 5,

FIG. 7 is a fragmentary sectionlike FIG. 5 showing another example of the invention,

FIG. 8 is a view on the arrow 8 in FIG. 7,

FIG. 9 is another sectional view through an annular flame tube showing yet another embodiment of the invention,

FIG. 10 is a similar section showing a further embodiment of the invention,

FIG. 11 is a fragmentary sectional view showing yet a further embodiment of the invention,

FIG. 12 is a view on the arrow 12 in FIG. 11,

FIG. 13 is a section of another annular flame tube incorporating yet a further embodiment of the invention,

FIG. I4 is a section on line 14-14 in FIG. 13,

FIG. 15 is a section like FIG. 13 showing yet another embodiment of the invention.

FIG. 16 is a section on line 16-16 in FIG. 15,

FIG. 17 is a sectional view illustrating a still further embodiment of the invention,

FIG. 13 is a section of a primary combustion air inlet variable flow restrictor,

FIG. 19 is a view on arrow X in FIG. 18; and

FIGS. 20 to 26 are views showing alternative forms of primary combustion air inlet variable flow restrictors.

DETAILED DESCRIPTION OF THE INVENTION Referring firstly to the embodiment shown in FIGS. 1 to 4 of the drawings, the flame tube incorporates an inner annular passage 30 for the primary combustion air, a surrounding annular passage 31 for secondary combustion air and an outer annular passage 32 for the dilution air. The passage 30 has an annular intake 33 whereas the passage 31 has a pair of annular intakes 34, 35 disposed respectively inside and outside the intake 33. A row of vanes 36 are mounted in the intake 33 and rows of vanes 37, 38 are likewise mounted in the intakes 34, 35 respectively. The vanes 36, 37 and 38 are on a series of common shafts arranged so that when the vanes 36 lie in planes parallel to the axis of the engine, the vanes 37, 38 are offset and vice versa. Thus when positioned as shown in full lines in FIG. 2 the primary combustion airflow will be restricted while the secondary combustion airflow will be substantially unrestricted.

The vanes, are, however, associated with pneumatic actuators 39 associated with pipework 40, 41 whereby the vanes can be turned to the positions shown in dotted lines in FIG. 2 such that the vanes 36 scarcely restrict airflow into the intake 33 whereas the vanes 37, 38 restrict airflow into the intakes 34, 35. As will be seen from FIG. 3.the actuators 39 are arranged to turn alternate ones of the shafts on which the vanes are mounted in one direction and the remaining shafts in the opposite direction so that no swirl is introduced either into the primary combustion air or secondary combustion air.

FIG. 4 shows how a single valve 42 can be employed to control the supply of compressed air to the pipework 40, 41 and the exhausting of air therefrom to enable all the vanes 36, 37, 38 to be adjusted simultaneously.

Turning now to FIGS. 5 and 6, the flame tube has a series of primary air inlets 50 each provided with swirler vanes which are known per se. Secondary combustion air is introduced via inwardly directed nozzles 51, of which there are two in association with each of the primary air inlets. Dilution air is introduced at two stages in the flame tube, mainly through a first series of nozzles 52 downstream of the nozzles 51 and through a second series of nozzles 53 downstream of the nozzles 52. The nozzles 53 are supplied via ducts 54 which open into intakes upstream of the nozzles 51. The flame tube si provided with axially movable deflector vanes 55 which can be moved from the positions shown in FIG. 5 in which they cover the intakes to the ducts 54, to positions in which they cover intakes to the secondary combustion air nozzles 51.

Referring now to the examples shown in FIGS. 7 and 8, the basic layout of the flame tube is similar to that shown in FIG. I, that is to say there is an annular primary air duct 60 surrounded externally by a III'SI secondary air duct 61 and internally by a second annular secondary air duct 62. There are also dilution air passages 63, 64 respectively outside the duct 61 and inside the duct 62.

For controlling the proportions of primary and secondary air there are provided three annular flow restricting members 65, 66, and 67. These three restrictors are joined together by means of radial arms 68 so as to be movable axially relative to the flame tube by means of rods like the rod 69. At one limit of the travel, as shown in FIG. 7 the annular restrictors 65, 66

restrict the entry of secondary combustion air to the ducts 61, i

62 respectively. In this position the restrictor 67 is deep inside the duct 60 and provides little restriction of the airflow therethrough. It will be noted, however, that the duct 60 diverges markedly from its intake so that when the restrictors are moved the their other position (as shown in dotted lines in FIG. 7) the restrictor 67 will provide a considerable restriction in the intake of the duct 60, whereas the restrictors 65, 66 will have little effect on the airflow into the ducts 61., 62 respectively.

In the example shown in FIG. 9 the secondary air intake is defined by an outer tube 70 and an inner tube 71. The outer tube 70 lies outside an inner tube 72 forming the outer wall of the primary air duct the inner wall 73 of which is outside the tube 71. The primary/secondary combustion air proportions are varied by means of a pair of annular rows of flaps 74, 75. These flaps are pivoted on tangential axes and when, as shown in FIG. 9 the outer row of flaps 74 are pivoted inwardly and the inner row of flaps 75 are pivoted outwardly there is a minimum area for primary airflow and a maximum area for 

1. An annular section flame tube for a gas turbine engine comprising an annular chamber having an annular primary combustion air inlet passage and at least one coaxial annular secondary combustion air inlet passage opening into said chamber downstream of said primary combustion air inlet passage, and airflow restricting means at the upstream ends of said passages displaceable in one direction to increase the intake area of the primary combustion air inlet passage and simultaneously to decrease the intake area of the secondary combustion air inlet passage and movable in the opposite direction to decrease the intake area of the primary combustion air inlet passage and simultaneously to increase the intake area of the secondary combustion air inlet passage.
 2. An annular section flame tube for a gas turbine engine comprising an annular chamber having an annular primary combustion air inlet passage and at least one coaxial annular secondary combustion air inlet passage opening into said chamber downstream of said primary combustion air inlet passage, and airflow restricting means at the upstream ends of said passages displaceable in one direction to increase the intake area of the primary combustion air inlet passage and decrease the intake area of the secondary combustion air inlet passage and movable in the opposite direction to decrease the intake area of the primary combustion air inlet passage and increase the intake area of the secondary combustion air inlet passage, a tubular wall separating said primary combustion air inlet passage from said secondary combustion air inlet passage, said airflow restricting means comprising a plurality of flaps arranged in an annular row at the upstream end of said tubular wall and pivoted on axes tangential to said wall and means for displacing said flaps in one direction across the secondary combustion air inlet passage and in the opposite direction across the primary combustion air inlet passage.
 3. An annular section flame tube as claimed in claim 2 in which the secondary combustion air inlet passage surrounds the primary combustion air inlet passage.
 4. An annular section flame tube as claimed in claim 3 further comprising an additional annular secondary combustion air inlet passage arranged coaxially within the primary combustion air inlet passage and divided therefrom by a further tubular wall, further flaps arranged in an annular row at the upstream end of said further tubular wall and pivotable on axes tangential to said further tubular wall, and further means for displacing said further flaps outwardly across the primary combustion air inlet passage and inwardly across the additional secondary combustion air inlet passage.
 5. An annular section flame tube as claimed in claim 4 in which said means for displacing said flaps and said further means for displacing said further flaps comprise the combination of a common axially movable structure, means connecting said structure to said flaps for inward displacement thereof by axial movement of said structure in one direction and outward displacement of the flaps by axial movement of the structure in the opposite direction and means connecting said further flaps to the structure for outward displacement of said further flaps by axial movement of said structure in said one direction and inward displacement of said further flaps by axial movement of said structure in the opposite direction. 